But I'm not sure how to make the data available to DEoptim when expfun is passed. What is the correct way to do this?

EDIT: Here is some (mock) data I can provide... I am not so familiar with R but am interfacing with it through python at the moment. A small clip of my input matrix, data, looks like this (from a pandas dataframe):

x y

0 33.8 19.734328

1 34.2 19.855713

2 34.4 20.005075

3 36.0 20.023766

4 36.1 20.921509

5 36.3 21.505115

6 36.6 24.600343

7 36.8 25.424239

8 37.4 26.335077

9 38.2 26.421332

10 41.6 26.729980

11 42.4 35.006403

12 46.0 37.647034

13 47.3 38.058187

14 47.8 38.177062

15 58.5 41.061019

16 79.1 43.005465

My data is loaded in through two numpy arrays x and y (again python) into a FloatVector: